A novel fluidized bed respirometric technique for determination of in situ biofilm kinetics

A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles - particles with attached biomass. Lava rock particles of 600 m were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (μ_max) of 3.69 ± 0.44d^-1 and biomass yields (Y_H) of 0.36 ± 0.03g COD/g COD in the fluidized bed respirometers were significantly different from the μ_max of 5.57-5.72d¹ and Y_H of 0.54-0.59g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (K_S) of 186-219mg COD/L observed in the fluidized bed respirometers relative to the 49-58mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16d ^-1 for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5g COD/g VSS.